Move ios documentation from //docs to //docs/ios.

docs/ios/infra.md

 # Continuous build and test infrastructure for Chromium for iOS
 
 See the [instructions] for how to check out and build Chromium for iOS.
 
 The Chromium projects use buildbot for continuous integration. This doc starts
 with an overview of the system, then gives detailed explanations about each
 part.
 
 [TOC]
 
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 After compilation, the bot will upload three artifacts. First the
 `Chromium.breakpad` symbols will be uploaded to
 `gs://my-gcs-bucket/<buildername>/<buildnumber>/Chromium.breakpad`. Next
 `Chromium.app` will be tarred, gzipped, and uploaded to
 `gs://my-gcs-bucket/<buildername>/<buildnumber>/Chromium.tar.gz`. Finally
 the `Chromium.breakpad` symbols will be uploaded to the [breakpad] crash
 reporting server where they can be used to symbolicate stack traces.
 
 If `artifact` is a directory, you must specify `"compress": true`.
 
-[analyzer]: ../tools/mb
+[analyzer]: ../../tools/mb
 [breakpad]: https://chromium.googlesource.com/breakpad/breakpad
 [buildbucket]: https://cr-buildbucket.appspot.com
 [chromium.fyi]: https://build.chromium.org/p/chromium.fyi/waterfall
 [chromium.mac]: https://build.chromium.org/p/chromium.mac
-[clang]: ../tools/clang
+[clang]: ../../tools/clang
 [commit queue]: https://dev.chromium.org/developers/testing/commit-queue
 [gitiles]: https://gerrit.googlesource.com/gitiles
-[GN]: ../tools/gn
-[instructions]: ./ios_build_instructions.md
+[GN]: ../../tools/gn
+[instructions]: ./build_instructions.md
 [iOS recipes]: https://chromium.googlesource.com/chromium/tools/build/+/master/scripts/slave/recipes/ios
-[iOS simulator]: ../testing/iossim
+[iOS simulator]: ../../testing/iossim
 [recipe module]: https://chromium.googlesource.com/chromium/tools/build/+/master/scripts/slave/recipe_modules/ios
 [recipes]: https://chromium.googlesource.com/infra/infra/+/HEAD/doc/users/recipes.md
 [simulator]: https://developer.apple.com/library/content/documentation/IDEs/Conceptual/iOS_Simulator_Guide/Introduction/Introduction.html
-[src/ios/build/bots]: ../ios/build/bots
-[src/ios/build/bots/scripts]: ../ios/build/bots/scripts
+[src/ios/build/bots]: ../../ios/build/bots
+[src/ios/build/bots/scripts]: ../../ios/build/bots/scripts
 [swarming]: https://github.com/luci/luci-py/tree/master/appengine/swarming
 [swarming server]: https://chromium-swarm.appspot.com
-[test runner]: ../ios/build/bots/scripts/test_runner.py
+[test runner]: ../../ios/build/bots/scripts/test_runner.py
 [tools/build]: https://chromium.googlesource.com/chromium/tools/build
 [try job access]: https://www.chromium.org/getting-involved/become-a-committer#TOC-Try-job-access
 [try server]: https://build.chromium.org/p/tryserver.chromium.mac/waterfall
 [tryserver.chromium.mac]: https://build.chromium.org/p/tryserver.chromium.mac/waterfall
 [universal binary]: https://en.wikipedia.org/wiki/Universal_binary
 [xctest]: https://developer.apple.com/reference/xctest